In the field of photomechanical process technology, photographic materials with excellent original-reproducibility, stable processing solutions and simplified replenishment system are required to deal with diversified and complicated print forms.
Originals to be employed in a line image photography processing are often composed of phototypesetting letters, hand-writing letters, illustrations and halftone dot image photographs. Accordingly, on original contains several images having a different concentration and a different line width in combination. Photomechanical cameras and photographic materials suitable for obtaining images from such originals with good reproducibility, as well as image-forming methods applicable to such photographic materials, are needed in this technical field. On the other hand, in the photomechanical processes for producing catalogs or large-sized posters, the blow-up or reduction of dot image photographs is widely employed. In the photomechanical processes involving enlarged dot images, the dots may be coarsened to give blurred photoprints. As opposed to this, in the photomechanical processes involving reduced photoprints, fine dots with an enlarged ratio of lines/inch are to be photographed. Accordingly, an image-forming method with a much broader latitude is desired for the purpose of maintaining the reproducibility of halftone dot images in the photomechanical processes.
As the light source for a photomechanical camera, a halogen lamp or a xenon lamp is employed. In order to obtain a sufficient photographing sensitivity to the light source, the photographic material used in the photomechanical process is generally ortho-sensitized. However, it was found that the ortho-sensitized photographic materials are much more influenced by the chromatic aberrations of the lens and therefore the quality of the images formed is frequently reduced by those aberrations. It was also found that the deterioration of the image quality is more noticeable where a xenon lamp is used as the light source.
As a system of satisfying the demand for a broad latitude, a method is known where a lith-type silver halide photographic material composed of silver chlorobromide (having a silver chloride content of at least 50% or more) is processed with a hydroquinone-containing developer in which the effective concentration of the sulfite ion therein is drastically lowered (generally, to 0.1 mol/liter or less) to obtain thereby a line image or halftone dot image having a high contrast and a high blackened density in which the image portions and the non-image portions are clearly distinguished from each other. However, the method has various drawbacks. Specifically, since the sulfite concentration in the developer to be employed in the method is low, development is extremely unstable to aerial oxidation. For the purpose of stabilizing the activity of the processing solution, various means must be effected. The processing speed is extremely slow, and the working efficiency is poor under the current state of the art.
Accordingly, an improved image-forming system is desired, which is free from the instability in image formation in the above-mentioned development method (lith-development system) and which may be processed with a processing solution having an excellent storage stability, to give photographic images having super-high contrast photographic characteristics. As one example, a system of forming a super-high contrast negative image having a gamma value of more than 10 has been proposed, for example, in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606 and 4,311,781. In that system, a surface latent image-type silver halide photographic material containing a particular acylhydrazine compound is processed with a developer which has an excellent storage stability and which contains a sulfite preservative in an amount of 0.15 mol/liter or more, under a pH of from 11.0 to 12.3. The proposed image-forming system is characterized by the fact that a silver iodobromide or silver chloroiodo-bromide-containing photographic material can be processed, although only a high silver chloride content silver chlorobromide photographic material can be processed by a conventional super-high contrast image-forming method.
The proposed image-forming system is excellent in that an image with a sharp halftone dot image quality is formed, the process proceeds stably at a high speed, and the reproducibility of the original is good. However, a further improved system with further elevated original reproducibility is still desired for the purpose of satisfactorily dealing with diversified print forms.
JP-A-61-213847 and 64-72140 illustrate examples of a photographic material system containing a hydrazine compound and also containing a redox compound capable of releasing a development inhibitor. (The term "JP-A" as used herein means an "unexamined published Japanese patent application".)
However, incorporation of a redox compound capable of releasing a development inhibitor into a super-high contrast photographic system containing a hydrazine compound results in the problem of a reduced gamma (.gamma.) value. In order to obtain a sufficiently high contrast (.gamma.&gt;10) in the super-high contrast photographic system, the amount of the hydrazine compound to be added thereto may be increased or a highly active hydrazine compound may be incorporated into the system or chemically sensitized silver halide emulsions may be used to constitute the system, but black pepper in the photographic material may occur.
On the other hand, examples of photographic materials of containing silver chlorobromide grains are described in JP-A-60-83028, 60-112034, 62-235947 and 63-103232.